Headspace technology is a relatively new technique which allows the sampling of the vapor of a material, so that the vapor may be analyzed using a gas chromatograph or other analytical instrument. The volatile (liquid or solid) material attains equilibrium with the vapor phase within a sealed vial. Equilibrium is established when the level of liquid or solid material in the vial no longer changes so that the total quantity of liquid or solid, and vapor remains constant. A syringe is then used to retrieve a small amount of vapor for analysis. Headspace technology is advantageous over conventional direct sample injection because it assures that only vapor enters the gas chromatograph. This is advantageous because it reduces the chance of contamination or destruction of the instrument due to introduction of unevaporated sample. Since the sample is in the vapor form, a larger sample size is possible. An increased sample size generally results in increased sensitivity.
The unique quality and character of many products are rooted in the chemical volatiles which comprise their odor. The ability to reliably measure and identify impurities, taints and adulteration is therefore valuable in many situations. Analytical techniques such as gas chromatography are sometimes used but data is often difficult to correlate with sensory information and is costly to produce. The Aromascan.RTM. technology produced by Aromascan Technologies allows odors to be measured electronically. Measurement of aromatic characteristics is very useful in certain applications.
A conventional Aromascan(& system is comprised of a sensory array and a gas sampling device that presents vapor of the sample material into connection with the array. The system is controlled and the data generated from array signals using an attached computer. The technology can recognize differences in the aroma, and hence the quality, of incoming raw materials. The ability to recognize or differentiate between a characterized product and an unknown imparts a wide range of potential applications for technology. The speed, sensitivity and accuracy of the technology translate into improved productivity and reduced costs.
Unfortunately, since this type of analysis is relatively new, there is still much needed improvement. Current Aromascan.RTM. sensors do not provide a means to control the rate of passage of sample materials before the sensor array. This lack of control translates into decreased sensitivity since the vapor for analysis travels too rapidly or slowly in front of the sensor array. An improper rate of travel in relation to the sensor array results in a lack of repeatability and potentially inaccurate results. Other types of analytical instruments may also benefit from better control of the flow of sample material thereto.
Thus, there exists a need for an apparatus and method to control the rate of travel of sample vapors in relation to a sensor array of an analytical instrument. There further exists a need for an apparatus which provides a controlled rate of flow of material collected from a sample into relation with the sensors of an analytical instrument.